The present invention relates to an optical head device or an optical pickup device used for optical disk systems to optically perform recording, reproduction and erasure of information such as data, image and music.
An important problem in the optical recording and reproducing art relates to the need for an optical head device which can be manufactured with a simple structure and at as low cost as possible. Generally, for optical recording and reproduction of information, a focus error signal and a tracking error signal are detected on the basis of light spots formed on photodetectors by light beams from an optical recording medium such as an optical disk. The diameters of the spots of beams for the detection of the focus error signal and the detection of the tracking error signal are required to be different from each other, thereby requiring provision of two photodetectors at different positions. The provision of the two photodetectors at the different positions causes complication of the arrangement of the optical system, and this can result in deterioration of the detection accuracy concurrent with increase in the manufacturing cost. Thus, a further improvement in terms of the arrangement of the optical head device would be required from the viewpoint of decrease in the manufacturing cost.